Good Question: Why Does The Cold Sap Our Car Batteries?

MINNEAPOLIS (WCCO) — It is a rite of passage in Minnesota. After a frigid night, the car will not start in the morning.

So, why does the cold sap our batteries?

“When you contacted me about this, the first thing I did is I jumped on Twitter and said, ‘Hey guys, I need some help,'” said Andy Rundquist, a physics professor at Hamline University. “It wasn’t so much not understanding how it works. It’s like, there’s so much involved!”

Car batteries are just less efficient when it is cold. For a battery to generate an electric current, there must be connection between positive and negative terminals. Chemical reactions that generate electrons are started when those terminals connect. Electrons then supply the current.

(credit: CBS)

“You just need a little bit of charge transfer, you basically need the electrons to go from one side to the other,” Rundquist said.

That process needs to happen fast. When it is cold outside, everything moves slower.

“The battery in the car hasn’t really lost the charge, the charge is there. It just can’t get out,” Rundquist said.

People might also notice cellphone batteries do not keep charge as well in the cold. Rundquist says cellphone batteries do work better than the liquid-based car batteries.

All kinds of batteries, whether they are in liquid and solid state, work differently. But Rundquist says the general notion is the same: two different chemical reactions transferring charge from one side to the other.